Preparation of n-substituted hydrazine derivatives



United States PREPARATION OF N -SUBSTIT UTED HY DRAZINE DERIVATIVES David W. Lam and Irving L. Mador, Cincinnati, Ohio,

assignors to National Distillers and Chemical Corporation, New York, N.Y., a corporation of Virginia No Drawing. Application September 23, 1957 Serial No. 685,416

5 Claims. (Cl. 260-583) This invention relates to a method for preparing derivatives of hydrazine. More particularly, the invention pertains to a process for producing hydrazines having N- substituted acyclic or cyclic hydrocarbon groups.

Recent interest in the use of hydrazine derivatives in the field of jet propulsion and for the preparation of various nitrogen-containing compounds has led to a search for a method of preparing hydrazine derivatives which is capable of being employed on a commercial scale. The

processes proposed heretofore have involved either expensive reactants or elaborate reaction and recovery steps.

One object of the present invention is to provide a com mercially attractive process for the preparation of hydrazine derivatives. Another object of the invention is to provide a process which avoids the difficulties of the prior art processes and at the same time results in high yields of hydrazine derivatives. Further objects of the invention will become apparent from the ensuing de scription.

In accordance with the invention, it has been found "that various derivatives of hydrazine may be prepared U RNHCONHCl-l-ZNaOH RNHNH +NaCl+NaHCO wherein R is an acyclic or cyclic hydrocarbon radical having from about 1 to 18, preferably about 1 to 8, carbon atoms. More specifically, R may be a straight or branched chain alkyl radical, having from about 1 to 18 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, heptyl, octyl, isoctyl, decyl, dodecyl, and etc. The alkyl radical may also contain such functional groups as hydroxyl, ether and any other group which does not interfere in the reaction. When hydrazine derivatives having a cyclic substituent are desired R may be either cycloalkyl, aryl, alkaryl or heterocyclic radicals such as cyclopropyl, cyclobutyl, cyclohexyl, cyclooctyl, phenyl, toluyl, xylyl, phenyl methyl, phenyl ethyl, furyl, pyridyl, pyrryl, thiophenyl, etc. As will be seen from the above equations, the R substituent in the hydrazine derivative product will correspond to the R substituent in the substituted urea employed as the feed material. In general, alkyl or aryl mono-substituted ureas, e.g. methylurea and phenylurea, are the preferred feed material.

The substituted ureas capable of being employed as the starting material in the process of this invention may be obtained from any known source. For example, Belgian Patent No. 450,541 indicates that methylurea may be proatent O duced by the direct reaction of methylamine and urea under pressure. Other possible methods for producing methylurea include refluxing a mixture of methylamine hydrochloride with an excess of urea or by the reaction of alkali cyanates with methylamine. As will be understood, the method of preparing the substituted urea feed does not constitute an essential feature of this invention.

In addition to the particular reactants employed, the present invention also involves carrying out the reaction under controlled operating conditions. To begin with, the temperature at which the reactants are initially mixed has been found to be critical. In general, it has been discovered that the reactants, should be mixed at temperatures within the range of about 5 C. to 20 C., preferably about 0 C. to 5 C. In preparing alkyl monosubstituted hydrazines, for example, best results were obtained when separate aqueous solutions of sodium hydroxide and alkyl urea were mixed with the subsequent addition of a cold sodium hypochlorite solution. The reaction mixture is then heated to a temperature of about 10 C. to 100 C., preferably about 60 C. to 100 C., and held at this elevated temperature for about /2 to 2 hours to complete the reaction. If, on the other hand, the reactants were mixed at elevated temperatures, i.e. about 60 C. to C., little or no hydrazine derivative was produced regardless of the order of mixing. It has also been found that if the mixed cold reactants are allowed to stand for a prolonged period of time before being heated to the reaction temperature, noticeably reduced yields of the hydrazine derivatives are obtained.

The exact reaction temperature employed will, of course, depend upon the particular reactants involved. As set forth above, the reaction temperature may vary from about 10 C. to C., the high temperature being somewhat preferred for the preparation of certain derivatives such as the alkyl mono-substituted hydrazine. When aryl substituted hydrazines are being prepared, lower reaction temperatures are sufiicient for the rearrangement reaction. Thus, for example, the reaction of phenylurea with sodium hypochlorite will take place below 20 C.

Though at least two moles of sodium hydroxide are required for each mole of substituted urea employed, in practice it was found that good results were obtained when from about 3 to 10 moles of sodium hydroxide were used for each mole of substituted urea. Even when the mole ratio ,was 20 to 1 yields as high as 48 percent were achieved, while maximum yields were obtained at a mole ratio of about 8 to l. The sodium hypochlorite solution can have a concentration in the range of about 3 to 20 percent, though a range of 5 to 15 percent is preferred. The mole ratio of sodium hypochlorite to substituted urea will generally be about 1:1. Though an excess of sodium hypochlorite was found to be beneficial in obtaining high yields, its presence was found to be somewhat detrimental during recovery of the hydrazine derivative product by distillation. More particularly, it was found that excess sodium hypochlorite would destroy some of the hydrazine derivative product. It is necessary, therefore, to destroy or otherwise remove the excess of sodium hypochlorite from the reaction product mixture prior to distillation. One method found to be effective was the addition of materials such as sodium thiosulfate, or sodium sulfite to the reaction product mixture to destroy the excess sodium hypochlorite. Other methods for removing excess sodium hypochlorite may also be employed. It is also within the scope of this invention to carefully control the excess of sodium hypochlorite employed in the reaction, eg about 5 to 25 percent, so that the usual side reactions would completely utilize the initial excess of this reactant.

ipotassiurn iodate.

The invention will be more fully understood by reference to the following illustrative examples:

Example I mlxof 5.17 percent sodium hyp'ochlorite solution (0.0350 M mole) was also cooled to less than C. over a period This mixture was then heated to 80 of about 20 minutes and maintained at 80 C. 'forzo'ne hour. -Atthe end of this period the reaction mixture was cooled, diluted to 100 ml. and titrated with standard Indicated yield was 0.0191 :mole methylhydrazine or 70 percent of theory based 'on methylurea used. 'Methylhydrazine was identified as-the 'sulfate (M.P. l41-142 C.) and picrate (M.P. 166 C.). Literature values'for these melting points-are 142 C.-'and 166 C., respectively.

Example 11 20. g. of methylurea (0.270 mole) 'was dissolved in 50 ml. of water and cooled to cless than C. To this was added 80 g. of sodium hydroxide (2.0 moles) dissolved in 150 ml. of water and againcooled. To the above mixture 500ml. of cold 5.17 percent sodium hypochlorite solution (0.350 mole) was added. On mixing the reactants were heated to 80 C. for one hour, cooled to room temperature and an'aliquot titrated with standard potassium iodate. The indicated yield of methyhydrazine was 0.198 mole or 73 percent based on starting methylurea. Thez reaction-mixture was distilled without destroying -excess.zhypochlorite. The first 50ml. of distillate was set aside and the product in .the remainder precipitated as "the sulfate by adding -'an excess of-sulfuric acid and redncing 1th 6a .syrup. Hydrazinesulfate wasrec'overed by dissolving the syruprin a minimum of water and then add- --ing:suflicient concentrated sulfuric-acid to make the soluxfionapproximately 30% in sulfuric. After filtering of the insoluble hydrazine sulfate, the methyl hydrazine sulfate was'precipitated by adding 8 volumes of ethanol:

Hydrazinersulfate 0.92 gm., 2.9%; M.P. '248250 C.

10 percent aqueous sodium hydroxide added. Then "-7.0

of cold 5.1-7 percent sodium hypochlorite (0.0049 'mole) was added, the reactants mixed-and permitted t'o 'C.1and added.

'ture by warm up to room temperature. On titration with standard potassium iodate a yield of 0.00091 mole phenyl-hydrazine was indicated, or 18 percent based on hypochlorite used. The phenylhydrazine was identified by isolation of the cinnamaldehyde derivative, M.P. 167l68 C. This melting point in the literature is 168 C.

The above data show .that..substituted hydrazines may be prepared readily in accordance with the process of this invention. It will be understood that the substituted hydrazinesmay be separated from the reaction product mixsuch conventional methods as distillation, final dehydration with caustic, etc. Other hypochlorites-such as t-butyl hypochlorite may also be employed in the reaction. The choice of solvents employed will depend, of course, upon their chemical stability and boiling point as well as their solubility properties.

While particular embodiments of the invention are shown-above, it will be understood that the invention is obviouslysubject to scope .of the-above description and the following appendvariance and modification within the ed claims.

What is claimed is: 1. A method ofpreparing hydrazine derivatives having the-formula RNHNH wherein R is an'alkylgroup having'from 1 to '18'carbon atoms, which comprises mixing'a mono-substituted'urea having the formula RNHCONI-I whereinR is saidalkyl group, with sodium hypochlorite t-and sodium-hydroxide at a reduced temperature 'ofabout --'5 -to 20 0., immediately allowing the resulting reaction to proceed at a temperature of about 10 to C. to, produce said-hydrazine derivatives.

2. The method of claim 1 wherein R is an alkyl group .haviug from -1 to 8 carbon atoms.

.3. Themethod of claim 1 wherein 'said mono-substituted urea is methylurea.

.dium thiosulfate.

References Cited in the file of this patent FOREIGN PATENTS Germany Dec. 10, 1942 Germany Apr. 20,1953 

1. A METHOD OF PREPARING HYDRAZINE DERIVATIVES HAVING THE FORMULA 